Techniques in tissue metabolism. 1. A mechanical chopper

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Abstract
A machine is descr. which produces slices and suspensions of fresh tissues with minimum disruption of cellular structure. It produced slices of several animal tissues down to 0.2 mm. in thickness, and prisms down to 0.067 x 0.67 mm. in cross-section. It has been applied to liver, spleen, kidney, adrenal, lung, heart, abdominal wall, skin, and especially to tissues of the central nervous system. Prisms 0.2 x 0.2 mm. in section and 2 mm. long can be made conveniently from many tissues in 30 sec. These can be suspended in salines, and sampled as a suspension. Many such suspensions were made from rat, guinea pig, and human cerebral hemispheres, and compared metabolically with slices or "homogenates" from the same tissues. In a glucose saline suitable for respiration of tissues, the chopped material respired at rates with 3% of those of ordinary hand-cut slices, and much more rapidly than "homogenates." Respiration by the mechanically chopped tissue was stable with time over a period of at least 2 hrs., during which that of "homogenates" fell considerably. Aerobic accumulation of lactic acid was similar to, but in some cases greater than in systems with slices. The rates at which mechanically chopped cerebral cortex respired and formed lactic acid were doubled or trebled by the electrical impulses which induced such changes in sliced cerebral cortex. Hence structure which is lost in "homogenates" is largely retained in the chopped prepns. The method is especially applicable to preparing biopsy and other small specimens of tissue for metabolic examination of processes which are controlled by structural factors.